Professor Pan Wenshi and his two doctoral students, Wang Dezhi and Ran Wenzhong, presented their major achievements in six years of research on the white-headed langur to delegates.

Pan and his team found the natural refuges of the leaf monkey was the region north of the Sifangling Mountain Range and south of the Zuojiang River in the southern Guangxi Zhuang Autonomous Region. This was smaller than their previous estimate.

About 700 to 800 white-headed leaf monkeys are currently isolated in seven zones in the area and live in the tropical monsoon evergreen broad-leaf secondary forest around the karst limestone hills.

"The seven areas are the last natural refuges of the monkey," the professor said.

However, only two of these areas could support a growing population of the monkey.

One is their field research area in Chongzuo County, which covers an area of 24 square kilometers (9.3 square miles). A total of 25 bands and troops of more than 250 langurs constitute the largest local population of the primate species.

Conservation work lasting six years has indicated numbers will continue to grow.

"Now infants and subadults constitute 70 percent of the local population," said Pan. "It means a wide expansion in numbers is possible in future."

Another area is the Longning Hills in Fusui County, which neighbors Chongzuo. Four relatively independent local populations are scattered in this area, with a total population of about 380 monkeys. Although they must vie for survival with the Rhesus monkeys (Macaca mulatta), researchers believe there is great potential for langurs to survive in the wild there if they are given proper protection.

About 100 white-headed langurs live in the other five areas. With a small local population (about 20 on average), Pan said the monkeys are facing environmental and hereditary pressures and their chances of continuing their existence in the wild is dim.

As well as learning about the current status, population number, structure and distribution of the monkeys, the researchers have collected basic data on the monkeys' population dynamics, social behavior and mating system.

"These data can help us to estimate the development prospects of the local population of the monkeys and provide a scientific basis for the protection of the primate," Pan said.

They have recorded some special social behavior of the monkey over the years, such as infanticide.

According to the professor, a male dominates a langur troop like a Godfather, but the stabilizing core of each troop is composed of female relatives who often remain together in the same home range throughout their lives.

Since most breeding troops contain only one fully adult male, competition between males for this position is fierce.

Encroaching males are chased away from the troop. But occasionally an invader will be successful in driving out the resident male and usurping his troop. Unweaned infants may be attacked, sometimes fatally, by incoming males.

In March 1998, a successful invader was seen attacking and killing an unweaned infant.

Since mothers who lose their offspring become sexually receptive sooner than mothers who rear their infants to weaning age, the professor said this indicates the killing of infants by incoming males is an evolved reproductive strategy.

"While eliminating the offspring of his competitors, the usurping male enhances his own opportunity to breed," he explained.

In February 2000, researchers observed a troop of 28 monkeys splitting because of an invasion by an adult male.

The defeated male, crippled by the usurpation, left with his sons, the eldest being three years old. The son, now aged five and sexually mature, lived with his father and helped him take care of his brothers.

Why the monkey has chosen to look after his family rather than search for his own chance to breed is being researched by Pan's team.

"The behavior might have some connection with altruistic behaviors of our human beings," Pan said. "It is truly worthy of further observation and research."

At the conference, the professor reached an agreement with two German biologists from Cuc Phuong National Park in Viet Nam for co-operation in research. In September, Pan will lead his team on a visit to the national park in Viet Nam.

"There are several different primate species living in the Vietnamese national park," he said. "In the future, we will make some comparative research to further our understanding of the white-headed langur."

(China Daily August 26, 2002)